"We are treating the deaths as suspicious", Toronto Police Constable David Hopkinson said in a phone interview.
Several Canadian newspapers say they were told investigators were working on the assumption Mr Sherman had killed his wife before killing himself.
Hopkinson declined to officially identify the victims, but statements from Apotex and politicians across the country on Friday named the Shermans as the deceased.
The family of a Canadian billionaire and his wife have hit back at reports surrounding their recent deaths.
Prime Minister Justin Trudeau and his wife Sophie Gregoire Trudeau were among those to offer a tribute to the couple through social media.
Police were called to the Shermans' home in an upscale neighbourhood of north Toronto just before noon on Friday in response to a "medical complaint".
"We are shocked and think it's irresponsible that police sources have reportedly advised the media of a theory which neither their family, their friends nor their colleagues believe to be true", the Shermans' children said.
In a statement, Apotex said Sherman grew the company from its "humble" roots to become a successful pharmaceutical firm with 6,000 employees in 21 sites across Canada.
Canadian Business magazine estimated Sherman's worth at $4.77 billion Canadian (US$3.65 billion).
Sherman, who had a PhD in astrophysics from MIT, was chairman of the closely held Canadian generic-drug maker and formerly chair of Cangene Corp., a Canadian biotechnology firm. Those include manufacturing and research facilities concentrated in the Toronto area as well as in Winnipeg.
Sherman "gave his life to the singular objective of our organization-innovating for patient affordability", Apotex said in the statement.
"Patients around the world live healthier and more fulfilled lives thanks to his life's work, and his significant impact on healthcare and healthcare sustainability will have an enduring impact for many years to come", the statement read. "As employees, we are proud of his tremendous accomplishments, honored to have known him, and vow to carry on with the Apotex goal in his honor".
Linda Frum, a Canadian senator who recently awarded a medal to Honey Sherman for community service, was among those paying tribute to someone she described as one of the most beloved members of Canada's Jewish community. The couple were found in their home, which was up for sale. Neighbours confirmed that the property was the couple's home.